Magnesium base alloy



Patented Nov. 12, 1940 UNITED STATES PATENT OFFICE MAGNESIUM BASE ALLOY No Drawing. Application November 13:1939,

Serial No. 304,133

3 Claims. (cits-16s) The invention relates to magnesium base alloys. It more particularly concerns alloys of this nature having a high degree of formability, associated with other improved physical properties, such as increased tensile and yield strengths.

Magnesium alloys are being widely used in various structural and mechanical arts where alight weight metal is highly desirable, such as for use in making castings, forgings, and the like. Howl ever, the use of these alloys in the rolled form to make sheet metal articles requiring forming operations, such as bending, drawing, and the like, has not progressed as rapidly due to thefact that, in general, alloys having good formabillty,

l permitting relatively sharp bends to be made without the articles developing external cracks, usually have inferior strength characteristics.

It is, accordingly, the principal object of the invention to provide a magnesium base alloy go which can be made into a rolled sheet or the like, possessing suflicient ductility or formability to be sharply bent, drawn, or otherwise shaped, while having improved tensile and yield strengths. :5 Other objects and advantages will be apparent as the description of the invention proceeds.

My invention resides in the discovery that a magnesium base alloy composed of from 0.5 to per cent of silver, 0.05 to l per cent of calcium, 1

1y high tensile strength and yield strength, is obtained when the alloy contains from 0.5 to 5 per cent of silver, 0.1 to 0.3 per cent of calcium, 6 'to ,12 per cent of cadmium, and from 0.5 to 5 per cent of zinc.

The specific proportion of each alloying metal and the total amount of the added alloying met-- als to be employed in the new alloy depends upon the use for which the alloy is intended. In general it is preferable to use alloys containing more 10 than about 80 per cent magnesium and less than per cent of the added metals. For example,

- in alloys where a high ductility or formability associated with high yield and tensile strengths is of principal importance, the total added metals 1 should not materially exceed about 7 per cent; while in those instances where exceptionally high yield and tensile stregnths are desirable-the percentage of total added metals should be above about 12 per cent.

The following table, which lists some of the properties of rolled sheet metal made from my new alloy, as well as the properties. of rolled sheet metal made from related quaternary alloys, illustrates the improvement in strength characteristics of the new alloy over that of some of the closely related alloys. In the table, the percent elongation is to be regarded as a measure of the ductility of the specimen.

Table Nominal composition in per- 7 cent (remainder- 'Annesled 001d rolled magnesium) 5 85 4 Yield Tensile Percent Yield Tensile Percent Ag Ce Zn 0d strength strength eio etion strength strength elon ation in lbs./sq. in. in lbs. /sq.in. in 2 ches in lbs./sq. in. in lbs/sq. in. in 2 chcs o. 9 o. 3 o. 9 26. 000 as, 000 11 45, 000 52-, 060 5 0.9 0. 9 5.0 18,000 as, 000 20 so, 000 42, 000 2 40 0. 8 0. 3 5. 1 22, 000 36, 000 20 38, 000 46, 000 3 0.9 0.8 0.9 4.7 30,000 41,000 10 44,000 60,000 2 4.7 0.3 2.5 20,000 36,000 13 40,000 52,000 4 4. 6 0. 3 4 8 19, 000 39, 000 19 46. 000 53, 000 3 5. 2 0. 3 2. 5 5 4 23, 000 41, 000 16 48, 000 55, 000 3 to 15 per cent of cadmium, and from 0.1 to 10 per cent of zinc, the balance ,being substantially all magnesium, is endowed with the aforementioned properties. While the properties of good formability or ductility, associated with high tensile and yield strengths, are manifest over the entire range of composition indicated, I have found that, in general, the preferred combination of properties such as the most desirable ductility for forming operations, coupled with exceptional- The properties listed in the above table under the section headed by the term annealed" were obtained by first rolling the alloys at a temperature between about 500 to 600 F., and thereafter annealing them at various temperatures through a temperature range of from 400 to 800 F. The properties selected for the table were those of the annealed specimens which exhibited the maximum elongation. The properties listed under the section headed cold rolled were obtained by subjecting specimens of the alloys which had been hot rolled at a temperature of from 500 to 600 F. to additional rolling in the cold state to bring about a total reduction in thickness of from 2 to 10 per cent. The properties selected for the table were those of the cold rolled specimens which showed the greatest tensile and yield strengths, while having at least a 1 per cent elongation in 2 inches.

By comparison of the "properties listed in the above table, it will be observed that the combined properties of my new polynary alloy are superior to those of the parent quaternary alloys having a similar percentage of alloying ingredients. For example, it will be noted that the compositions containing the' lower percentages of alloying ingredients have greatly improved e1on-. .gation, coupled with superior yield and tensile properties in the annealed state, while those havv amenable to solution and precipitation heat treatments, which, accordingly, modify its properties.

The new alloy may be compounded in any of the ways known to the art, such as by adding the ingredients to molten magnesium under suitable flux. The flux should be substantially free from magnesium chloride if the calcium content of the alloy is to be above 0.3 per cent. In those instances where an alloy is to be compounded containing less than 0.3 per cent of calcium, magnesium chloride may be presentin the flux without exerting undue deleterious effects, but in this case it is usually preferable to add the calcium last and without too much stirring or agitation in order that the loss of calcium into the flux will be substantially prevented.

I claim:

1. A magnesium base alloy containing from 0.5 to 10 per cent of silver, 0.05 to 1 per cent of calcium, 1 to 15 per cent 01 cadmium, and from 0.1 to 10 per cent of zinc, the balance being magnesiuml 2. A magnesium base alloy containing from 0.5 to 5 per cent of silver, from 0.1 to 0.3 per cent of calcium, from 6 to 12 per cent of cadmium, and from 0.5 to 5 per cent of zinc, the balance being magnesium.

3. Amagnesium base alloycontaining from 1 to 5 per cent of silver. from 0.1 to 0.3 per cent of calcium, from'6 to 8 per cent of cadmium, and

from 1 to 5 per cent oi zinc, the balance being magnesium.

JOHN C. MCDONAID. 

